Biological diversity is an umbrella term for the degree of nature's variety, including both the number and frequency of ecosystems, species, or genes in a given assemblage. It is usually considered at three different levels, "genetic diversity," "species diversity," and "ecosystem diversity." Genetic diversity is a concept of the variability within a species, as measured by the variation in genes (chemical units of hereditary information that can be passed from one generation to another) within a particular species, variety, subspecies, or breed. Species diversity is a concept of the variety of living organisms on earth, and is measured by the total number of species in the world (variously estimated as from 5 to 30 million or more, though only about 1.4 million have actually been described), or in a given area under study.

In general, the larger the population size of a species, the greater the chance of there being high genetic diversity. But population increase in some species may lead to a population decline in other species, and even to a reduction in species diversity. Since it is usually not possible to have both maximum species diversity and maximum genetic diversity, national policy-makers should define the optimum biological diversity consistent with their development objectives; one key element is to ensure that no species falls below the minimum critical population size at which genetic diversity is lost rapidly. Ecosystem diversity relates to the diversity and health of the ecological complexes within which species occur.

Ecosystems provide natural cycles of nutrients (from production to consumption to decomposition), of water, of oxygen and carbon dioxide (thereby affecting the climate), and of other chemicals like sulphur, nitrogen, and carbon. Ecological processes govern primary and secondary production (i.e., energy flow), mineralization of organic matter in the soils and sediments, and storage and transport of minerals and biomass. Efforts to conserve species must therefore also conserve the ecosystems of which they are a part.

Back...